[PATCH 4.19 114/140] pvcalls-front: dont return error when the ring is full

[Greg Kroah-Hartman]

From: Stefano Stabellini <sstabellini@xxxxxxxxxx>

[ Upstream commit d90a1ca60a1eccb4383fe203c76223ab4c0799ed ]

When the ring is full, size == array_size. It is not an error condition,
so simply return 0 instead of an error.

Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/xen/pvcalls-front.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index 3a144eecb6a72..d7438fdc57061 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -504,8 +504,10 @@ static int __write_ring(struct pvcalls_data_intf *intf,
 	virt_mb();
 
 	size = pvcalls_queued(prod, cons, array_size);
-	if (size >= array_size)
+	if (size > array_size)
 		return -EINVAL;
+	if (size == array_size)
+		return 0;
 	if (len > array_size - size)
 		len = array_size - size;
 
-- 
2.20.1